The present invention relates to a heat pump and a dehumidifying apparatus, and more particularly to a heat pump with a high COP and a dehumidifying apparatus which has such a heat pump and a high moisture removal per energy consumption.
As shown in FIG. 11, there has heretofore been available a dehumidifying apparatus having a compressor 1 for compressing a refrigerant, a condenser 2 for condensing the compressed refrigerant with outside air, an evaporator 3 for depressurizing the condensed refrigerant with an expansion valve 5 and evaporating the refrigerant to cool process air from an air-conditioned space 10 to a temperature equal to or lower than its dew point, and a reheater 4 for reheating the process air, which has been cooled to a temperature equal to or lower than its dew point, at the downstream side of the condenser 2 with the refrigerant upstream of the expansion valve 5. The refrigerant is condensed in the condenser and the reheater. With the illustrated dehumidifying apparatus, a heat pump HP is constituted by the compressor 1, the condenser 2, the reheater 4, the expansion valve 5, and the evaporator 3. The heat pump HP pumps heat from the process air which flows through the evaporator 3 into the outside air which flows through the condenser 2.
Here, operation of the heat pump HP shown in FIG. 11 will be described below with reference to a Mollier diagram shown in FIG. 12. The diagram shown in FIG. 12 is a Mollier diagram in the case where HFC134a is used as the refrigerant. A point a represents a state of the refrigerant evaporated by the evaporator 3, and the refrigerant is in the form of a saturated vapor. The refrigerant has a pressure of 0.34 Mpa, a temperature of 5xc2x0 C., and an enthalpy of 400.9 kJ/kg. A point b represents a state of the vapor drawn and compressed by the compressor 1, i.e., a state at the outlet port of the compressor 1. In the point b, the refrigerant is in the form of a superheated vapor. The refrigerant vapor is cooled in the condenser 2 and reaches a state represented by a point c in the Mollier diagram. In the point c, the refrigerant is in the form of a saturated vapor and has a pressure of 0.94 MPa and a temperature of 38xc2x0 C. Under this pressure, the refrigerant is cooled and condensed to reach a state represented by a point d. In the point d, the refrigerant is in the form of a saturated liquid and has the same pressure and temperature as those in the point c. The saturated liquid has an enthalpy of 250.5 kJ/kg. The refrigerant liquid is depressurized by an expansion valve 5 to a saturation pressure of 0.34 MPa at a temperature of 5xc2x0 C. A mixture of the refrigerant liquid and the vapor at a temperature of 5xc2x0 C. is delivered to the evaporator 3, in which the mixture removes heat from process air and is evaporated to reach a state of the saturated vapor, which is represented by the point a in the Mollier diagram. The saturated vapor is drawn into the compressor 1 again, and the above cycle is repeated.
Operation of the dehumidifying apparatus shown in FIG. 11 will be described below with reference to a psychrometric chart shown in FIG. 13. In FIG. 13, the alphabetical letters K, L, M correspond to the encircled letters in FIG. 11. Air (in a state K) from the air-conditioned space 10 is cooled to a temperature equal to or lower than its dew point to lower the dry bulb temperature thereof and lower the absolute humidity thereof, and reaches a state L. The state L is on a saturation curve in the psychrometric chart. The air in the state L is reheated by the reheater 4 to increase the dry bulb temperature thereof and keep the absolute humidity thereof constant, and reaches a state M. Then, the air is supplied to the air-conditioned space 10. The state M is lower in both of absolute humidity and dry bulb temperature than the state K.
With the conventional heat pump and dehumidifying apparatus described above, since it is necessary to considerably cool the air to its dew point, about half of the refrigerating effect of the evaporator in the heat pump is consumed to remove a sensible heat load from the air, so that the moisture removal (the dehumidifying performance) per electric power consumption is low. If a single-stage compressor is used as the compressor in the heat pump, then it produces a one-stage compression-type refrigerating cycle, resulting in a low coefficient of performance (COP) and a large amount of electric power consumed per amount of moisture removal.
It is therefore an object of the present invention to provide a heat pump with a high coefficient of performance (COP) and a dehumidifying apparatus which consumes a small amount of energy per amount of moisture removal.
According to an aspect of the present invention, as shown in FIG. 1, for example, there is provided a heat pump comprising: a pressurizer 260 for raising a pressure of a refrigerant; a condenser 220 for condensing the refrigerant to heat a high-temperature heat source fluid; an evaporator 210 for evaporating the refrigerant to cool a low-temperature heat source fluid; and heat exchanging means 300 disposed in a refrigerant path connecting the condenser 220 and the evaporator 210, for evaporating and condensing the refrigerant under an intermediate pressure between the condensing pressure of the condenser 220 and the evaporating pressure of the evaporator 210 to cool the low-temperature heat source fluid by evaporation of the refrigerant under the intermediate pressure and to heat the low-temperature heat source fluid by condensation of the refrigerant under the intermediate pressure; wherein the low-temperature heat source fluid is successively cooled by the heat exchanging means 300, cooled by the evaporator 210, and heated by the heat exchanging means 300 in the order named.
Preferably, the heat exchanging means 300 is arranged such that the refrigerant is repeatedly evaporated and condensed alternately under the intermediate pressure. Typically, the refrigerant condensed by the condenser 220 to heat the high-temperature heat source fluid is the refrigerant pressurized by the pressurizer 260, and the refrigerant evaporated by the evaporator 210 to cool the low-temperature heat source fluid is pressurized by the pressurizer 260.
With the above arrangement, the heat pump comprises the heat exchanging means for evaporating and condensing the refrigerant under an intermediate pressure between the condensing pressure of the condenser and the evaporating pressure of the evaporator to cool the low-temperature heat source fluid by evaporation of the refrigerant under the intermediate pressure and to heat the low-temperature heat source fluid by condensation of the refrigerant under the intermediate pressure. Therefore, the low-temperature heat source fluid is successively cooled by the heat exchanging means, cooled by the evaporator, and heated by the heat exchanging means in the order named. Hence, the low-temperature heat source fluid can be precooled by the heat exchanging means prior to cooling in the evaporator, and the low-temperature heat source fluid which flows out of the evaporator can be heated with use of the heat in precooling.
According to another aspect of the present invention, there is provided a heat pump, wherein the intermediate pressure includes at least a first intermediate pressure and a second intermediate pressure lower than the first intermediate pressure, and the heat exchanging means 300 cools the low-temperature heat source fluid successively by evaporation of the refrigerant under the first intermediate pressure and by evaporation of the refrigerant under the second intermediate pressure in the order named, and the heat exchanging means heats the low-temperature heat source fluid successively by condensation of the refrigerant under the second intermediate pressure and by condensation of the refrigerant under the first intermediate pressure in the order named.
With the above arrangement, since a heat exchange is performed between the counterflows of the low-temperature heat source fluid, the heat exchanging means can achieve a very high efficiency of heat exchange.
According to still another aspect of the present invention, as shown in FIG. 1, for example, there is provided a dehumidifying apparatus comprising: a pressurizer 260 for raising a pressure of a refrigerant; a condenser 220 for condensing the refrigerant to heat a high-temperature heat source fluid OA; an evaporator 210 for evaporating the refrigerant to cool process air to a temperature equal to or lower than its dew point; heat exchanging means 300 disposed in refrigerant paths 107-111 connecting the condenser 220 and the evaporator 210, for evaporating and condensing the refrigerant under an intermediate pressure between the condensing pressure of the condenser 200 and the evaporating pressure of the evaporator 210 to cool the process air by evaporation of the refrigerant under the intermediate pressure and to heat the process air by condensation of the refrigerant under the intermediate pressure; and a process air path connecting the heat exchanging means 300 and the evaporator 210 such that the process air is successively cooled by the heat exchanging means 300, cooled by the evaporator 210, and heated by the heat exchanging means 300 in the order named.
Typically, the refrigerant condensed by the condenser 220 to heat the high-temperature heat source fluid is the refrigerant pressurized by the pressurizer 260, and the refrigerant evaporated by the evaporator 210 to cool the low-temperature heat source fluid is pressurized by the pressurizer 260
Typically, the high-temperature heat source is ambient air, and the low-temperature heat source fluid is precooled in the heat exchanging means 300 prior to cooling in the evaporator 210. The low-temperature heat source fluid may be condensed by the heat exchanging means 300 while being precooled. Preferably, the heat exchanging means 300 is arranged such that the refrigerant is repeatedly evaporated and condensed alternately under the intermediate pressure. The heat exchanging means 300 may further be arranged such that the intermediate pressure includes at least a first intermediate pressure and a second intermediate pressure lower than the first intermediate pressure, and the heat exchanging means 300 cools the low-temperature heat source fluid successively by evaporation of the refrigerant under the first intermediate pressure and by evaporation of the refrigerant under the second intermediate pressure in the order named, and the heat exchanging means 300 heats the low-temperature heat source fluid successively by the condensation of the refrigerant under the second intermediate pressure and by condensation of the refrigerant under the first intermediate pressure in the order named. The dehumidifying apparatus may comprise a bypass path for delivering the refrigerant condensed by the condenser 220 to the evaporator 210 in bypassing relation to the heat exchanging means 300, as shown in FIG. 8, for example.
According to still another aspect of the present invention, as shown in FIG. 1, for example, there is provided a dehumidifying apparatus comprising: a pressurizer 260 for raising a pressure of a refrigerant; a condenser 220 for condensing the refrigerant; an evaporator 210 for evaporating the refrigerant to cool process air to a temperature equal to or lower than its dew point; and heat exchanging means 300 for precooling the process air at the upstream side of the evaporator 210 which cools the process air and reheating the process air at the downstream side of the evaporator 210 which cools the process air; wherein the refrigerant before being introduced into the evaporator 210 is supplied to the heat exchanging means 300.
Typically, the refrigerant condensed by the condenser 220 to heat the high-temperature heat source fluid is the refrigerant pressurized by the pressurizer 260, and the refrigerant evaporated by the evaporator 210 to cool the low-temperature heat source fluid is pressurized by the pressurizer 260.
According to still another aspect of the present invention, as shown in FIG. 8, for example, the dehumidifying apparatus may further comprise a bypass path 401 for delivering the refrigerant condensed by the condenser 220 to the evaporator 210, and the bypass path may bypass the heat exchanging means 300.
With the above arrangement, since the dehumidifying apparatus comprises the bypass path, in the case where the moisture contained in the low-temperature heat source fluid is to be removed by cooling the low-temperature heat source fluid with the evaporator, the relationship between the temperature and humidity of the low-temperature heat source fluid can appropriately be adjusted.
There may also be provided a dehumidifying apparatus having the heat pump, the low-temperature heat source fluid being process air, the evaporator 210 being arranged so as to cool the process air to a temperature equal to or lower than its dew point, and an air path connecting the heat exchanging means 300 and the evaporator 210 such that the process air is successively cooled by the heat exchanging means 300, cooled by the evaporator 210, and heated by the heat exchanging means 300 in the order named.
The present application is based on Japanese patent application No. 11-330431 filed on Nov. 19, 1999, which is incorporated herein as part of the disclosure of the present application.
The present invention can more fully be understood based on the following detailed description. Further applications of the present invention will become more apparent from the following detailed description. However, the following detailed description and specific examples will be described as preferred embodiments only for the purpose of explaining the present invention. It is evident to a person skilled in the art that various changes and modifications can be made to the embodiments in the following detailed description within the spirit and scope of the present invention.
The applicant has no intention to dedicate any of the embodiments described below to the public, and any of the disclosed modifications and alternatives which may not be included in the scope of the claims constitutes part of the invention under the doctrine of equivalent.